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US 4,791,889 AGranted
Steam temperature control using a modified Smith Predictor
AssigneeThe Babcock & Wilcoc Company
InventorsTheodore N. Matsko, Robert S. Rand, Thomas D. Russell, Thomas J. Scheib, Robert R. Walker, deceased
Life of this patent
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Abstract
A system for controlling steam temperature in a boiler using a time delay feedback controller known as a Smith Predictor to provide control tuning of true boiler parameters which change with load.
Claims5
A steam temperature controller comprising:
- a feedforward predictor for presetting an expected secondary superheater inlet temperature with a boiler load and for generating a secondary superheater inlet temperature cascade controller set point;
- a first modifier means for correcting said expected first temperature for the deviation between a firing rate required for the boiler load and an actual firing rate;
- a second modifier means for correcting said expected inlet temperature for deviation of an air flow rate required for the firing rate for the boiler load and an actual air flow rate;
- a third modifier means for correcting said expected inlet temperature for reheat temperature control;
- a feedback correction control means for final correction;
- and
- a cascade control means responsive to said inlet temperature for providing rapid process loop response to predictable intermediate process control points.
4 more elements
A method of controlling the temperature of steam in a boiler comprising the steps of:
- presetting an expected secondary superheater inlet temperature with a boiler load;
- generating a secondary superheater inlet temperature cascade controller set point;
- correcting said expected inlet temperature for the deviation between a firing rate required for the boilder load and an actual firing rate;
- correcting said expected inlet temperature for the deviation of an air flow rate required for the firing rate for the boiler load and an actual air flow;
- correcting said expected inlet temperature for reheat temperature control;
- providing final feedback correction of said inlet temperature;
- and
- providing rapid process loop response to said inlet temperature for rapid process loop response to predictable intermediate process control points.
5 more elements
Dependencies are inferred from the claim text.